Automatic hob shifter



July 9, 1963 G. DAVENPORT ETAL 3,096,686

AUTOMATIC HOB SHIFTER Original Filed July 5, 1957 4 Sheets-Sheet 1 g NE; (\l

INVENTORS 9 GRANGER DAVENPORT El By JOSEPH E. VAN ACKER AQWKM ATTORNEYJuly 9, 1963 G. DAVENPORT ETAL 3,096,586

AUTOMATIC HOB SHIFTER Original Filed July 5, 1957 4 Sheets-Sheet 2 mdE vRR.

T R m 00K TP C m? um X m0 V R E r P E MS em Y B WV 2 b. 5% 66C wn mwATTORNEY y 1963 G. DAVENPORT ETAL 3,096,686

AUTOMATIC HOB SHIFTER Original Filed July 5, 1957 4 Sheets-Sheet 3 y1963 G. DAVENPORT ETAL 3,

AUTOMATIC HOB SHIFTER 4 Sheets-Sheet 4 Original Filed July 5, 1957 o 0 aW m\ 2 mm m um um:

ATTORNEY a-ssasss United States Patent Ofifice 3,096,686 AUTOMATIC HOBSHIFTER Granger Davenport, Montclair, and Joseph E. Van Acker,

New Vernon, N.J., assignors to Norton Company,

Worcester, Mass., a corporation of Massachusetts Qontinuation ofapplication Ser. No. 670,200, July 5, .1957. This application Apr. 12,1962, Ser. No. 189,660

13 Claims. (Cl. 90-4) .Thepresent invention relates to bobbing machinesand more particularly to an improved method and means for periodicallyshifting the hob axially precise increments or multiples thereof wherebyto bring unused teeth of the hobintocuttin-g relation with the workblank, eventually to utilize all of the teeth of the hob before it isnecessary to remove and resharpen the hob.

This application is a continuation of my prior copending application,Serial Number 670,200, filed July 5, 1957, now abandoned.

A primary aim of the invention is to render available a :hobbing machinein which the hob-spindle bearings of a shiftable hob remain firmlyclamped to the swivel head during the cutting operations, and in whichthe mechanism provided for shifting the hob unit distances atpreselected times during a run of work incorporates means automaticallyoperable to vunclamp the hob-spindle bearings before effecting theshift, and to reclamp the hobspindle bearings firmly to the swivel headfollowing each shift movement of the hob. It is proposed further toprovide hob-shifting means in which the errors, if any, in theincrements of shift are noncumulative in effect on the total shift.Moreover, the instant invention provides a device with inherentflexibility and versatility that will enable an operator to initiallyzero the hob on a tooth or a space, and thereafter to obtain minute butexact increments of shift, or if desired, only approximately correctincrements of shift.

Another aim ofthe invention is to provide built-in hob-shifting meanswhose incremental shifts may be precisely controlled to suit the leadand tooth spacing of the hob and which may be operated to shift the hobprogressively selectively in either axial direction with means availablefor operation at the end of the total shift toreturn the hob spindlerelatively rapidly to its initial starting position for removal andreplacement by a sharp one.

,Another aim of the invention is to provide a selfcontained andprotected hob-shifting mechanism for hobbers which will performautomatically .to effect hob-shifting movements after one or a selectednumber of feed cycles have been concluded, and which is operativeautomatically to register the cycles and record the shifts and to imparta signal to the operator when the hob has been advanced incrementally apreset distance, usually the full distance that a given hob is capableof being advanced.

.Still another ,aim of the invention is to provide hobshifitinge meansthat is completely automatic in its action following an initialsetting-up operation, to the end of relieving-the operator of all manualcontrol or supervision in order that'he may devote his attentionexclusive to other operations and functions of the machine.

A further aim of the invention is to render available a hob-shiftingmechanism that is failure-safe, i.e., a mechanism that operatesautomatically to stop the machine should there be a failure in the powersource relied upon to effect hob clamping.

A further objective of the invention is the provision of an improvedhob-shifting mechanism that is substantially entirely enclosed andembodies a minimum of exposed parts "likely to become damaged or fouledby cutting Fatented July 9, 1953 chips or coolant liquids, or by beingaccidentally struck when mounting or removing the work.

In carrying forward the objectives of this invention it is proposed tomount the spindle bearings for lateral movement in the hob-swivel-headunit and to equip the head with built-in protected means operable tomaintain the hob-spindle bearings firmly clamped except when it isdesired to shift the hob at which time the bearings are unclamped. Toeffect shifting of the spindle bearings, driving and driven elementssuch as a rack and pinion or an equivalent screw and not are employed,the driven element being fast to one of the spindle bearings, and thedriving element being actuated in a forward or reverse direction bymeans of an adjustable-stroke fluid-actuated power cylinder andintermediate gearing including a ratchet mechanism, stroke-modifyingchange gears, and a direction-reversing gear cluster. The stroke of thepiston of the power cylinder is made variable by means of a graduatedstop operative to normally aiford shift increments from .010 to .080 in.in steps of .010 in. For exact increments of shift which do not coincidewith the .010 in. steps, provision is made for the insertion of pick offgears in the train between the ratchet device and the spindle bearing sothat a movement of the power cylinder Which would normally impart anexact shift in increment steps of .010 in. will result in incrementsteps of .010 in. times the ratio Driver/Driven. For example, apowercylinder movement which normally would result in an exact .OSO-in.shift will with a 44-tooth gear driving a 46- tooth gear produce anequally exact shift increment of .07652 in. Larger shift movements maybe imparted to the hob in accordance with this invention by theincorporation of a shift-increment multiplying element that functionsautomatically to cause the power cylinder to recycle its operation aselected number of times so that the total shift per cycle becomes amultiple of the previously determined unit increments.

Entrance of chips or other foreign matter to the shifting mechanism isprevented by enclosing all moving parts within the swivel head and bycontrolling the operation thereof by valves and switches externallylocated.

In conjunction with the foregoing, manual means may be provided toselect the direction of the automatic power shifting as well as toeffect the shifting manually. Additional control means have been soarranged that the cutting cycles between shifts may be selected, thehobshift movements may be counted singly or in multiple, and a signalgiven when a count indicative of a full complement of shifts for a givenhob has been reached. The device described herein also includes controlmeans operable to efiect a succession of shifts, i.e., to impart atraverse movement to the hob in one direction or the other.

A further aim of the invention is to provide means for automaticallyeffecting a hob-shifting movement at a point in the bobbing cycle inwhich such hob shifting can be carried out safely without requiring theoperators attention.

Other objects and advantages will be in part indicated in the followingdescription and in part rendered apparent therefrom in connection withthe annexed drawings.

To enable others skilled in the art so fully to apprehend the underlyingfeatures hereof that they may embody the same in the various wayscontemplated by this invention, drawings depicting a prefer-red typicalconstruction have been annexed as a part of this disclosure and, in suchdrawings, like characters of reference denote corresponding partsthroughout all the views, of which:

FIG. 1 is a side view of a representative hobbing machine embodying theinvention.

FIG. *2 is a detailed view of a hob-shift control panel used with thisinvention.

FIG. 3 is a front view of the hob swivel head illustrating more clearlyportions of the spindle-bearing mounting and clamping means.

FIG. 4 is an enlarged sectional view taken substantially along line 4-4of FIG. 3.

FIG. 5 is a sectional view of portions of the bearingshifting geartrain.

FIG. 6 is a sectional view of a preferred form of power cylinder andassociated mechanism. provided to effect the power shifting.

FIG. 7 is a vertical sectional view of a preferred form of ratchetmechanism responsive to the strokes of the power cylinder.

FIG. 8 is a plan view of a portion of the head illustrating portions ofthe change-gear drive to the spindle-bearing-shifting rack.

FIG. 9 is an elementary diagram of the pneumatic and hydraulic systemprovided to actuate the hob-shifting mechanism and the bearing clamps.

FIGS. 10, 10A, and 10B are elementary diagrams of the electrical-controlsystem.

Referring more particularly to FIGS. 1 and 3 of the drawings, thehobbing machine illustrated comprises a base 56 that provides bearingsfor a rotary work spindle 51, and a support for an upstanding stanchion52. The forward face of the stanchion is provided with vertical guides53 on which is mounted a vertically movable hob slide 54. The hob slidein turn carries an angularly adjustable hob swivel head 55 whichsupports laterally adjustable hob-spindle bearings 56 and 57. A hobspindle 59 is journaled in the bearings 56 and 57 and is adapted tomount a hob H in clamped position between suitable sized solid spacercollars 60, including, if desired, a micrometer-typeadjustable-thickness spacer 60a to enable initial settings to be mademore conveniently.

The letter W designates a stack of gear blanks that have been partiallyhobbed by the hob H. The blanks are mounted upon a suitable work-holdingfixture secured to the rotary table WT, and in a normal hobbing cycleboth the work and the hob are rotated in synchronisrn as the hob is fedaxially of the gear blanks. M designates the main-drive motor which isconnected by suitable gearing to drive the work and the hob. T is atraversing motor selectively connectable to propel the hob slide up ordown on the stanchion, and C is a coolant motor that operates a pump tosupply a coolant lubricant to the hob and Work during the hobbingoperation. The several transmissions alluded to have not beenillustrated in all their detail on the drawings for they may be ofconventional design and per se form no direct part of the instantinvention.

With reference more particularly to FIGS. 3, 4, and 5, which illustratefeatures of the hob swivel head in larger detail, it will be seen thatthe hob-spindle bearings 56 and 57 are semi-circular and cradled incomplementary shaped finished cavities 61 and 62 in the swivel-headcasting and that their longitudinal marginal edges are overlaid by clampstraps 63, 64, 65, and 66. The upper set of straps 63 and 64 arenormally secured in a fixed position, whereas, the lower set of straps65 and 66 are relieved at their undersides to form a toe portion 67 (inFIG. 4) that bears against the spindle bearings and a power-receivingend 69. A plurality of strap-mounting studs 70 pass through the clampstraps 65 and 66 at regions intermediate the toe portion 67 and thepowerreceiving end 69 and function as aligned fulcrum points about whichthe straps may be tilted so as to bring pressure upon the spindlebearings for clamping or to relieve the pressure thereon to permit thebearings to be shifted. The clamp straps 65 and 66 are given a slightcrown in their outer surface to make the fulcrums effective under thestud nuts.

One of the bearings, preferably the inner bearing 56,

is relieved at its rear to receive a section of a rack 71 which issecured to the bearing and meshed by a pinion 72 out on a transverselyextending shaft 73, as shown in FIG. 5. The shaft 73 is journalled inthe hob-swivelhead casting 55. The inner end of pinion shaft 73 has gearteeth 74 cut thereon adapted to be meshed by the teeth of a worm 75 on avertical shaft 76 that is also journalled Within the hob-swivel-headcasting, as shown in FIG. 5. Bevel gears 98 and 77 connect the shaft 76with a stub shaft 79 that projects to the front of the head andterminates in a clutch end 78 designed to receive a removable handcrank. When the clamp straps 65 and 66 are released, the hand crank maybe applied to the clutch end of the stub shaft 79 and a turning thereofwill effect a shifting of the hob-spindle bearings 56 and 57 and, aswell, the hob spindle 59 and the hob mounted thereon.

In accordance with this invention it is proposed to axially move the hobpreselected precision amounts by means of an air-operated cylinder 80built into the swivelhead casting 55. FIGS. 6, 7 and 8 illustrate apreferred construction of power cylinder in which the piston rod 81extends from the cylinder and is provided with rack teeth '82 thatcontinuously mesh with the teeth of a pinion gear 83. The pinion '83 ismounted to revolve freely on a ratchet shaft 86 and carries aspring-loaded radial pawl 91 positioned to engage teeth 86:: on theratchet shaft 86. A similar pawl 92 radially movable in a relativelyfixed member 92a, retains the ratchet shaft during the reset strokes ofthe power cylinder. The angular movement imparted to the ratchet shaft86 during the forward strokes of the power cylinder is transmitted togear 87 removably splined to the shaft 86, and thence through changegears 88 and 89 to a vertical shaft 76a that is coaxial with the wormshaft 76. The intermediate gear 88 of this train is mounted upon anormally fixed but adjustable arm 90 that is pivoted on the ratchetshaft 86. By rearranging these gears or by substituting others, theratio of power-cylinder movement to the movement of the coaxial shaft76a may be modified and precisely determined.

As illustrated more clearly in FIG. 4, the unidirectional movementimparted to the shaft 76a is transmitted to worm shaft 76 through themedium of a motion-reversing clutch mechanism consisting essentially ofa shiftable clutch spool 96 that is keyed to the shaft 76a and a groupof three bevel gears 97, 98, and 77. Gears 97 and 98 are provided withclutch teeth complementary to the teeth of the shiftable clutch spool.Gear 97 is loose on the coaxial shaft 76a, gear 98 is part of or may besecured to worm shaft 76, and the intermediate bevel gear 77 is keyed tothe manually actuated stub shaft 79. Clutch spool 96 is annulalrlygrooved to receive a shifting fork 100 on a spring-centered shaft 101(FIG. 6) whose upper end is grooved to receive an eccentric pin 102projecting from the end of a manually operable shaft 103. The shaft 103extends to the front of the swivel head and is provided with a controlknob 104 by means of which the shaft may be turned to cause theeccentric pin to operate the clutch shifter shaft 101 up or down fromneutral, which in turn operates the motion-reversing clutch from aneutral position to a hobshift-left position or to a hob-shi'ft-rightposition. Means in the form of a ball-and-dentent mechanism 105associated with the shaft 103 is provided to retain the clutch in anyone of its three operative positions, i.e., manual shift, power-shiftleft, or power-shift might.

Through the transmission just explained, it will be seen that any givenstroke of the power cylinder 80 and its rod 81 may be caused to shiftthe hob-spindle bearings a precise distance depending upon the selectionof change gears 87, 89, and in either direction depending upon thesetting of the direction control knob 104. The extent of axial-shiftmovement imparted to the hob may also be varied by varying the operatingstroke of the power cylinder and its rod 81. In the embodimentillustrated in the drawings, it is intended that the piston of the powercylinder always move on its power stroke to the end of the cylinder andcomet to a dead stop. At that time a limit switch 161.8, forming part ofthe control circuit, is engaged and actuated by the piston rod and thepiston is caused automatically to return. The extent of the returnmovement of the piston is made a variable distance by means of anadjustable increment rod 110. The rod 110 is tubular in form andexternally threaded so as to be moved axially within a rotatable gaugingnut 111 journalled in the swivel-head casting. One side of the incrementrod is flattened andgraduated as at 110a in uniform spaces indicative ofthe hob-shift distances, e.g., .010, .020, .030 and up to .080 in. whenthe ratio change gears 87-89 are 1:1. The rod 110 is adjusted in or outof the power cylinder to adjust the length of the stroke and thismovement is then translated into increment steps of .010 in. by reasonof the rack teeth 82 rotating the pinion $3 back so as to cause the pawl91 to pass an integral number of teeth 86a on the ratchet shaft 86. Eachtooth 86a passed on the reset stroke will result in a basic .010-in.shift during the forward stroke. The increment rod adjustment accuracyneed only be such as topick up the desired number of ratchet teeth. Theouter end of the tubular increment rod is capped and carries a limitswitch 17LS whose operating plunger is adapted to be actuated by anextension rod 112 secured to the piston of the power cylinder andoperative within the increment tube 110. The switch 17LS also forms apart of the control circuit that controls the flow of compressed airthrough lines .113 and 114- connected with the ends of the powercylinder 80.

Compressed air from any suitable source may be valved to the powercylinder by a system shown diagrammatically in FIG. 9. Air underpressure enters line 115 connected with a solenoid-operated reversingvalve 119 of standard design commercially available. Normally the valve119 is biased to the left position shown in FIG. 9 and pressure air isdirected to the rod end of the cylinder 80 through line 114 to hold thepiston retracted and to avoid creep. When, however, solenoid 121 isenergized, the valve is shifted to the right and pressure air isdirected to the large end of the cylinder through a restricting needlevalve 117 and line 113 and the piston moves, thereby advancing rack bar82 and turning pinion gear 83 of the bearing-shifting ratchet. Forwardmovement of the piston and rack bar continues until the piston of thepower cylinder stops at the end of the cylinder whereupon limit switch16LS is operated to de-energize valve solenoid .121 and the pistonretracts.

Reference number 117a in the line around the restricting valve 117 is abypass valve that is opened when shifting the hob uphill and the weightof the spindle assembly is against the pressure.

A further important feature and function of the hobshift mechanism isits flexibility in affiording an infinite variety of accurately measuredshift increments. Briefly, the limit switches 16LS and 17LS and thesolenoid 121 of the air valve 119 are elements of a control circuit thatincludes stepping switches and counters whereby the hobshift mechanismmay be caused to function at the end of one or a selected number ofbobbing cycles, to count the number of shifts made so that the hob maybe replaced when fully used, and increase the extent of hob shifting bymaking exact integer multiples of exact increments when desired. As tothis last-mentioned feature the following will serve as an example:Assuming the increment rod be set with relation to the end face of thenut 111 on line .050 and with change gears 87-89 of 1:1 ratio, thedistance the hob will be shifted on any one shift cycle will be .050 in.However, if the shift-cycle multiplier switch ZTS is set on #2, theshift cycle is auto matically repeated and the extent of hob shift willbe exactly .100 If the multiplier is set on #3 the shift increment willbe repeated 3 times, giving a total-shift of .150 in. in any one shiftcycle. The flollowingttableishows the rangeof shift increments madepossibleby this invention:

Standard Hob-Shift Increments Automatic H0b-Sliift Attachment IncrementRod Multi- Increment Rod Multi- Setting plier Setting plies 010 l 060 5020 1 080, 4 030 l 0 70 5 040 1' 060 6' 050 l 080 5 060 1 070' 6 070 '1050 9 .080 l osn gs 030 3 070 7 050 2 050 10 060 2 0501 '0 070 2 080 i 7050 3 060 10 080 2 070 9 060 3 080- i 8 050 a 070 10- 070 3 .080 '9' 0803 I080 10 050 5 The above table is based upon the use of change-gears87-89, giving a 1:1 ratio of movement. If, however, the shift incrementdesired in the preceding example were to be .0446 in. instead of 1050in., ratio'change gears are installed that produce this fraction of the.050 setting indicated by the increment rod. Such fractions may bemultiplied when desired by use of'the shift multi plier above explainedto obtain any exact imfltip'I'e 0fthe selected fraction.

Hob-Spindle-Bearing Clamping (FIGS. 3, 4, and 9 The spindle bearings ofthe present construction are clamped preferably by a hydraulic-fluidpressure system comprising lower clamp straps 65 and 66 of the spindlebearings. The rod end of the piston element 130 in each cylinder bearsdirectly on the power receiving end 69 of the respective clamp straps.Pressure fiuidfor acmating the pistons outwardly to effect a: rocking ofthe straps about the fulcrum points afiorded' by the mounting studs 70,whereby to efiect clamping of the spindle bearings, is derived from anair-operated booster pump or intensifier illustrated diagrammatically inFIG. 29-.- The intensifier unit consists essentially of an airoperatedpump section that drives an hydraulic pumpsection 12 1. Pressure airfrom the line 115 after passing a; pres-- sure regulator valve 122 isdirected to' the air motorhydraulic pump section 120. Thehydraulicpumptakes fluid from a reservoir R and passes it under.relatively high pressure through a nonreturn valve 123' to a solenoid-operated spring-returned valve 124. In the position shown in FIG. 9the valve is biased to tlieleft and high-pressure fluid is passedthrough a disconnect coupling 126 to line 127 Where itbranchesinto-five: separate lines leading to the respectiveclamp'cyhnders 12'8. When the solenoid ofthe valve is energized thevalveRshifts to the right against its spring and the fluid within eachclamp cylinder back flows through the'valve tothe'reservoir R. Acup-shaped spring 128a within each clamp cylinder assists the back flowof fluid and assures release 0; the clamp straps so that the spindlebearings may s ift.

Hob-Shift Limiting Stops (FIGS. 3 and 4) Shifting of the hob to theright or to the left an'excessive distance may be prevented by providingone of the hob-spindle bearings, preferably the main hob-spindle bearing56, with a stop pin arr-anged'to'operate between sets of adjustablecollars 136' and 137 mounted upon a rod 138. Rod 138 is secured atitsends in-em tensions of the upper-main-bearihg strap'63 and istherefore relatively fixed. Accordingly, if the attendant fails tochange the hob at the end of the total shift movement determined bypresetting the collars 136, '137, the pin 135 that travels with the mainhearing will come up against one of the sets of collars and stop theshifting movement. When that occurs the power cylinder will not completeits stroke, limit switch 16LS will not be.

actuated, and subsequent functions of the machine will not beinstituted.

Control (FIG. I)

This invention further proposes novel means for effecting incrementalhob shifts selectively automatically and manually, the automatic meansincluding in part the electrical switching means provided to control thehobbing cycle. trated, this includes in part a pair of spring-balancedswitch-operating rods 140 and 141 mounted along the stanchion forlimited vertical movement.

dogs 142 each adapted to be engaged by a slide-carried latch 145 toeifect lifting or lowering of the rod 140. Movement of the rod 140 in anupward direction eifects actuation of limit switch 3LS, and movement ina downward direction effects actuation of limit switch 418. Trip rod 141mounts adjustable dog 147 and extreme limit dogs 146 and 148 adapted tobe engaged by another slide-carried latch 149 and movement of the rod141 vertically actuates limit switch 1LS. The limit switches lLS, 3L8,and 4LS are mounted in an enclosure 150 and are instrumental incontrolling the cycle of operation of the machine and of thehob-shifting mechanism including a cycle-counting means located in acontrol panel 167 illustrated at the right end of the machine adjacentthe housing which contains the pneumatic and hydraulic equipmentpreviously explained and the electrical-control panel and circuitry nowto be explained.

Electrical System (FIGS. 10, A, 10B) MOTOR CONTROL In the diagrams FIGS.10, 10A, and 10B, the letters M, T, C, and D designate the mainadrivemotor, traverse motor, coolant motor, and chip-conveyor motor,respectively, each of which is controlled by a magnetic starter 1M, 2M,and 4M connected to heavy-duty power lines L1, L2, and L3. The mainpower lines L1, L2, and L3 are fed through a circuit breaker CBconnected as indicated in FIG. 10. A transformer 150 connected acrosslines 1L1 and IE3 supplies lower voltage to the control circuit that isfed by lines 151 and 152. The main-control circuit for the motor starterinitiates at line 152 and current is supplied through normally closedSTOP pushbutton 153 and normally closed COUNT switch 216 to the RUN-TOGswitch 154. When switch 154 is turned to RUN and thereby closed, acircuit is completed through DOWN button 156 and UP button 157 andnormally closed limit switch lLS to coil M1 of the starter of themain-drive motor M. If the COOLANT: OFF- ON switch 159 is ON a parallelcircuit is completed to coil M3 of the coolant-motor starter.

When the main-motor contactors close, a holding circuit around the RUNbutton is completed through contactor switch M1. Should the operatorturn the switch 154 to its 106 position and press the button, theholding circut becomes ineffective.

The traverse-motor control circuit starts at STOP button 153, and afterpassing normally closed limit switch 2LS and the TRAVERSE switch 155,assuming the latter to be closed on the RUN side, a pressing of the UPbutton -7 completes a circuit to the reverse coil 2R of the traversestarter through limit switch 3L8, and opens the circuit to coils M1 andM3 of the main and coolant motors M and C. When coil 2R is energized aholding In the vertical-feeding bobbing machine illus-' Rod 140 mountsadjustable dogs 143, 144, and two extreme limit 8. circuit is completedthrough contacts 2R around the UP button.

When the DOWN button 156 is pressed, a similar circuit is completedthrough limit switch 4L8 to the forward coil 2F of the traverse-motorstarter, and as before a holding circuit will be completed around theDOWN button through contacts ZF and the circuit to main and traversemotor coils Md and M3 will be interrupted. The establishment of aholding circuit is necessary in each instance, because UP button 157 andDOWN button 156 are of the momentary contact type.

Should the operator desire to jog the traverse motor and inch the hobslide up or down the TRAVERSE switch is turned to JOG which cuts out theholding circuit made by contacts 2R and 2F.

Limit switch 2LS is located in the base of the machine and is actuatedto :open position when the power-feed clutch-lever 160 is operated toengage the power feed to the hob slide that is driven from the mainmotor M through conventional bobbing-machine feed gearing (not shown).

Limit switches 1LS, 3L8 and 4LS are on the stanchion and are actuated inresponse to the vertical movements of the hob slide by means of the triprods and dogs previously mentioned. Switch 1LS is actuated by rod 141 tostop the main motor M when the slide reaches its preset bottom positionunder power feed. Switches 3LS and -4LS are double-contact double-throwand are actuated by trip rod 140 to stop the traverse motor at thepreset limits of the up-and-down traverse movements of the slide as wellas to control the action of certain elements of the hob-shiftingmechanisms and their control circuits as will now be explained.

HOB-SHIFT CONTROL In accordance with this invention, means and circuitryis provided to efiect the hob shifting automatically or manually, toelfect the shifting only after a preselected number of pieces have beencut by the hob, to effect the shifting either at the top or the bottomof hob-slide movement, and to .give warning and shut down the machine atthe completion of the total shift movement for that hob.

The electrical elements which are located at the operators controlstation on the stanchion 52 and which are manually set to control thehob shift are a four-circuit selector switch 200 having its circuitclosings controlled by a three-position cam, and a combinationpushbutton and selector switch 201.

The electrical elements which are located at the electrical componentenclosure and which are manually set are a multi-position selector tapswitch 1TS, a shift-cycle multiplier switch ZTS, a predeterminingcounter 204, and a pushbutton switch 205.

In a hobbing machine equipped for radial feeding, the hob shift occursalways at the point Where the hob is withdrawn radially from the Workand in this case, the operator is relieved of the necessity forselecting the point in the bobbing cycle at which the hob shift willoccur. However, in hobbing machines equipped for axial feeding only, itis necessary for the machine operator to select the point at which thehob will shift. For axial feeding up, hob shift preferably occurs whenthe hob slide 54 is returned to its lower-most position at the end ofthe cutting cycle, whereas for axial feeding down, hob shift preferablyoccurs when the hob slide 54 is raised to its upper-most position justprior to loading a new workpiece W. For this purpose, a selector switch206 is furnished at the operators control station on the stanchion whichpermits him to select the shift point at the top or the bottom of thehob-slide movement.

The selector switch 200 has one position which closes a set of circuitswhich effects a continuous hob shifting to rapidly move the hob-spindlebearings 56 and 57 to one extreme end of its movement, this switchposition being labeled RE. (RETURN). A second position of this selectorswitch closes a circuit to directly energize solenoid 125 of valve 124,and also removes all forward power from the hob-shift power cylinder 80via relay 20CR, this switch position being labeled UNCL. (UN- CLAMP).The third position closes a set of circuits which are normal for theoperation of the hob shift and is labeled CL. (CLAP).

The combination pnshbutton and selector switch 201 has one positionwhich closes a circuit which causes the hob shift to occur automaticallyat the correct point in the hobbing cycle, this position being labeledHOB shift: AUTO. The other position of this selector switch 201 allowsthe switch to operate as a pushbutton and when depressed, it initiates ahob-shift movement at a point other than during the hobbing cycle, thisposition being labeled HOB SHIFT: MANUAL.

Hobs do not always wear during the cutting of a single stack of gearblanks sufficiently to require the hob to be shifted. For this reason,selector tap switch [1T8 selects the number of stacks of gears to be cutbefore a hob shift occurs.

The control operation for automatic hob shifting is as follows:

The operator presets the selector switch 200 to the CLAMP position andthe selector-pushbutton switch 201 to HOB SHIFT: AUTO position. He thensets the dial of the loads-per-shift selector switch -1TS at anydesirable setting determined from his past experience with the amount ofwear which results from cutting a stack of gears; for example, he mayknow that cutting one stack of largerdiameter gears of heat-treatedsteel results in enough Wear top-revent satisfactory cutting on thesecond stack, so he will then set the switch ITS at the #1 position. Healso knows that the hob-tooth advance is exactly .090 in, so he setsincrement rod 110 to the .030- in. graduation mark and sets the dial ofmultiplier switch ZTS' to #3 position. His machine may not be equippedfor radial feed, and he may be feeding down, so he sets the selectorswitch 206 to automatically shift when the slide 54' is at itsupper-most position.

The operator proceeds to out a gear. The slide feeds down and the gearis finished when the hob leaves the blank at the bottom. The operatorunloads the gear from the machine and then causes the slide to traverseto its uppermost point so as to allow a new workpiece to be loaded. Assoon as the slide in its upward movement forming relay SCR. This relayis operated by DC. and

has a heavy single-turn winding at the armature end of the core whicheffectively slows the movement of the armature and delays the opening ofthe relay contacts so that a pulse having a duration of about .050second is formed. This pulse momentarily energizes the stepping relaycoil STEP 2, which advances the stepping switch wipers 210 one step tocontact terminal B1. and at the same time, the stepping switchoff-normal contact ON. 2 closes. Considering the stepping switch ofitself, each gear cut would cause the stepping switch wipers to progressfrom position B1 to B2 to 133, etc., while the offnormal contact ON. 2,closed only upon the initial step, remains closed until such time as theswitch is advanced all the way forward to the normal or zero positionwhen ON. 2 will open. However, since switch 1TS has been set to the #1position where the wiper 211 contacts its terminal B1 (B1 identifying awire not shown between the stepping switch. and tap switch 2T5) acircuit is set up .through ON. 2, to the stepping switch to terminals B1to ITS wiper to relay 19CR to ground wire #2 via the motor startercontacts M1. (Motor starter contacts M1 prevent hob'shift during theperiod of cutting of the gear.) When relay 19CR isenergized, 19CRcontacts bypass the stepping switch and tap switch and 19CR is therebyheld energized even if the stepping switch should move off the contactwhich originally energized 19CR. At the same time, other 19CR contactsclose a circuit through ON. 2 to the stepping switch self-interruptercontacts INT 2 to energize the coil of stepping switch. This mode ofenergization of the stepping switch causes the STEP 2 stepping switch tobuzz, advancing its wiper forward rapidly until the wiper reaches thenormal position at which ON. 2 opens the circuit and stops the steppingswitch in its off position. In the process of advancing to the normalposition, the stepping switch wiper passes over a few terminals 212after B24 which momentarily closes a circuit through ON. 2, 17LS, 16LS,and relay 20CR. 20CR being energized closes contacts ZOCR which bypassesON. 2, the stepping switch, and 17LS, and holds 20CR energized evenafter the stepping switch wipers move off the contacts which originallyenergized ZOCR. At the same time, this same 200R contact closes acircuit via 17LS limit switch to energize 21CR relay. 21CR relaycontacts energize valve solenoid 125 which causes the hob-spindlebearings to be unclamped, and 20CR re lay contacts energize thehob-shift valve solenoid 121 which causes air to be exhausted from therod end of the power cylinder and causes pressure air to be admitted tothe large end of the cylinder through line 113. 20CR relay contacts alsoclose in the circuit to the MINOR stepping switch coil circuit whichcauses the MINOR step wiper 213 to advance from its off position to theposition Al and at the same time, the minor off-normal contacts MINORO.N. close.

The power-cylinder piston starts to move and this move ment withdrawsrod 112 and allows 17LS to open. 20CR relay contacts still hold 20CRenergized, and the piston completes its movement, advancing thehob-spindle bearing .030 in., and at the end of its stroke, 16LS isoperated which opens the circuit to 200R, which then opens its contacts.The MINOR switch coil releases its armature, and the valve solenoid 121returns under its spring bias to reverse the directions of pressure andairflow to the power cylinder 80. MINOR O.N. contacts are still closedso that relay 21CR remains energized to hold the hob-spindle bearingsunclamped. The power-cylinder piston starts its reset strokeand 16LScloses. 20CR contact and 17LS are both open, so that closing of 16LSonly permits ZtiCR relay coil to be later energized. The pistoncompletes its movement and rod 112 operates to close 17LS. Thiscompletes a circuit through MINOR O.N. to 17LS to 1618 to 20CR whichcloses the bypass circuit through 20CR contacts. 20CR being againenergized causes the MINOR step wiper 213 to advance to position A2, andthe valve solenoid 121 again to become energized to cause a secondstroke of the power cylinder to advance the spindle hearings to .060 in.from its initial point. The reset stroke of the power cylinder acts thesame as it did on the previous reset stroke, and the power cylinderstarts on its third operating stroke. When 20CR is energized for thisthird operating stroke, the MINOR switch coil is energized and the MINORstep wiper advances to the position A3. 2TS tap switch is already set tothe third (-A3) position for a 3 multiplier and this causes the MINORreset coil to be energized.

The power cylinder completes its third stroke to advance the hob-spindlebearings .090 in. from its initial position and opens 16LS whichde-energizes 20CR. 20CR contacts open, de-energizing the MINOR coil, andsince the MINOR reset coil is energized, the wiper is returned to itsoff position. The MINOR switch wiper moving off the A3 positionde-energizes the MINOR reset coiland upon reaching the off position,opens the MINOR O.N. off-normal contacts. This all occurs so rapidlythat when the power-cylinder piston completes its third reset stroke andcloses 17LS, the circuit previously closed via MINOR O.N. is open and nofurther shifting occurs. MINOR O.N. being opened also de-cnergizes 21CRwhich de-energizes valve solenoid 125 which returns to its normalposition. High-pressure hydraulic fluid then operates to clamp thehob-spindle bearings. This entire three-stroke hob-shift cycle occurs inapproximately one second. i

Each time valve solenoid 125 is energized to unclamp the hob-spindlebearings to permit shifting, a counter coil 204 COUNT 2 is alsoenergized. This causes a predetermining counter 215 to record the numberof times that the hob is shifted, and when the hob has been shifted apredetermined number of times, the counter trips a contact 216 whichopens the starting circuit for the hobber. (The counter 215, in somerespects, duplicates the function of the system of stops previouslydescribed and may be eliminated if visual recording is not desired.) Atthe same time, a signal light 217 indicates that the hob is worn out andmust be changed. The operator must then remove the worn hob and replaceit with a sharp one and then return the hob-spindle hearings to theirstarting position. To return the spindle bearings to their startingpoint, the operator turns the handle 104 to the opposite direction fromthat used for shifting, and then turns the HOB: RETURN-CLAMP-UNCLAMPselector switch 2% to the RETURN position. This closes the circuit torelay 21CR which causes the hob-spindle bearing to be unclamped, closesthe circuit to 230R via 17LS and 16LS, and also opens the circuit to theMINOR stepping switch coil to prevent counting strokes or shifts. -Thehob-shift power cylinder 81) then continuously recycles to rapidly movethe hob-spindle bearings to the beginning point which is established bythe stop nuts 136 mounted on range rod 138. The hob-spindle hearing hasa short stub 135 projecting from its upper quarter which actscooperatively with the stop nuts to limit the extent of movement. Whenthis stub contacts the range-rod stop nuts, the power cylinder stallswith pressure still applied to the large end of the piston and all ofthe drive train will be under strain. It is now necessary that theoperator return handle 164 to the normal shifting direction, but due tothe strain on the drive train, this will not be possible until the airpressure is removed from the large end of the piston. To accomplishthis, the operator turns the HOB: RETURN-CLAMP-UNCLAMP selector switch200 to UNCLAMP which removes power from 200R relay which in turnde-energizes solenoid 121 of valve 119. Air pressure thereby removedfrom the power cylinder relieves the strain against the handle 104 andallows it to be turned to the direction required to shift the hobspindle.

When the handle 104 is turned in the proper direction, the HOB:RETURN-CLAMP-UNCLAMP switch 260 is turned to CLAMP. This causes thehob-spindle hearings to be clamped and places all circuits ready toshift. The operator then turns his HOB SHIFT: MANUAL-AUTO pushbuttonselector switch 201 to MANUAL and momentarily depresses the pushbutton.This causes 20CR to be energized and causes the hob-spindle bearings tobe shifted. This effectively removes all backlash from the drive train,and the operator then turns his selector switch 201 back to AUTO for thenormal automatic operation.

From the foregoing it will be seen that a novel hobshifting mechanismhas become available that is not only unique in its action butexceptionally versatile in its ability to perform the important hobshifting function under a wide range of hobbing conditions. Themechanism disclosed is fully protected against damage by chips,coolants, or other abuse by being self-contained and fully enclosedwithin the swivel-head casting. The head carries no bulky units ormechanisms likely to interfere with an operators close observation as towhether the machine is setup for rightor for left-hand helical-gearhobbing or whether it is setup for cutting with or against the feed. Themechanism is readily adaptable to effect the hob shifting innoncumulative precision increments over the whole range, upon obtainingthe initial hob zero position with the micrometer collar 60:: on the hobspindle and with the selection and installation of proper pick-01f gears8'7, 88 and 8? of which a wide range is available. Provision is alsomade for incremental shifting in either direction and likewise provisionis made for quickly returning the hob by power to its initial startingposition.

When set for automatic operation the shifting is completely automatic,the shifts occurring without attention on the part of the operator aftereach stack of gears or after a given number of stacks have been hobbed.The device functions automatically to shut down the machine when thepreset complement of shifts has been made and gives an appropriatesignal should the operator fail to note or be unaware that it is time tochange the hob.

During the hobbing periods between shifts, the hobspindle bearings aresecurely clamped; the machine may not be operated with the bearingsunclamped. Should there be a failure in the air pressure that motivatesthe hydraulic clamping system of the instant embodiment, pressure switchPPS illustrated schematically in FIGS. 9 and 10A opens the entirecontrol circuit and the machine stops. The entire system of controls ispushbutton and knob operated, all appropriated identified as tofunction, and requires a minimum of effort and skill on an operatorspart to manipulate.

Without further analysis, the foregoing will so fully reveal the gist ofthis invention that others can, by applying current knowledge, readilyadapt it for various utilizations by retaining one or more of thefeatures that, from the standpoint of'the prior art, fairly constituteessential characteristics of either the generic or specific aspects ofthis invention and, therefore, such adaptations should be, and areintended to be, comprehended within the meaning and range of equivalencyof the following claims:

What is claimed is:

1. The combination of a translatable slide member, a hob spindle, meansmounting said hob spindle for rotary and axial movement relative to theslide member, power-operated clamping means for said spindle-mountingmeans normally operative to retain the spindlemounting means in apreselected axially adjusted position, first power means for actuatingsaid clamping means, second power means adapted when actuated to effectaxial movement of said mounting means a preselected unit distance,selectively adjustable means to vary the preselected unit distance,independently operable control means for each of said first and secondpower means, and a coordinating system of controls responsive totranslation of said slide member and operative normally to effectoperation of said control means through one cycle including unclampingof said spindle-mounting means, then axial movement thereof, and then areclamping of the spindle-mounting means to the slide member, andadditional selectively operable means associated with said system ofcontrols for causing said system of controls to repeat the axialmovement portion of the cycle two or more times to thereby obtain two ormore preselected unit distances of movement of the mounting means beforereclamping of the spindle-mounting means.

2. In a hobbing machine having a rotary hob spindle adapted to support ahob and a rotary work spindle adapted to support a workpiece to beoperated upon by the lhOb and means for rotating the hob spindle and thework spindle in timed relation and simultaneously effecting relativemovement between the spindles in the direction of the teeth to be cut onthe workpiece, the combination of means mounting the :hob spindle foraxial displacement, clamp means normally operative to maintain the hobspindle in a preselected axially displaced position during theperformance of a hobbing operation, power means operatively connectedwith said hob spindle adapted when actuated to effect axial displacementof said hob spindle a unit distance, said power means comprising anadjustable-stroke power cylinder having a movable piston and meanscomprising an adjustable abutment member positioned in;the path ofvmovement of the piston for defining one end of the stroke of the pistonwhereby selectively and directly to control the unit distance said hobspindle is displaced on each operating cycle, and control meansresponsive to the said relative movement between the spindles forrendering said clamp means inoperative at a selected point in the saidrelative movement between the spindles and thereafter said power meansoperative to effect axial displacement of the hob spindle said unitdistance.

3. The combination of claim 2 characterized by the inclusion of ratiovarying means in the connections between the power cylinder and thedisplaceable hob spindle for modifying the effect of a preselectedlimited movement of the piston of the power cylinder on the extent ofhob spindle displacement to obtain fractional units of axialdisplacement.

4. The combination of claim 2 in which said power means operativelyconnected with the hob spindle for effecting axial displacement thereofincludes a one-wayoperating ratchet means connected to be driven fromthe piston of said power cylinder, and means selectively operable torender said ratchet means operable to effect hob-spindle displacement ineither direction on a power stroke of the cylinder so that on repeatedcycles of operation of the said clamp means and the said hob-spindledisplacing means the hob spindle is displaced in successive incrementsin the selected direction, and means op erative on the displacement ofthe hob spindle through a pre-selected distance for rendering said powercylinder ineffective.

5. In a hobbing machine having a reciprocable slide member adapted tocarry a rotatable hob spindle the combination of bearing meansdisplaceable in the direction of the axis of the hob spindle forjournalling the hob spindle to the slide member, bearing-clamping meanshoused in the slide member operative normally to clamp the hob-spindlebearing means in a preselected axially displaced position, power meansalso housed within the slide member and operatively connected with saidbearing means and adapted when actuated to displace said bearing meansfrom the said preselected position, means responsive to thereciprocatory movement of the slide member for counting the strokesthereof, and means operative when the slide strokes reach a selectedcount to effect cyclic actuation of said clamp means in a bearingunclamping direction and thereafter to effect actuation of said powermeans to effect the displacement of said bearing means, and meansoperative on the conclusion of the bearing displacement movement toagain effect actuation of the bearing clamp means in a bearing clampingdirection.

6. The combination set forth in claim 5 characterized by the inclusionin the combination of additional counting means responsive to adisplacement movement of the bearing means for recording the bearingdisplacement cycles and operative when a predetermining count is reachedto render said power means ineffective to produce further displacementof the said bearing means.

7. In a bobbing machine having a reciprocaible tool slide adapted tosupport a rotatable hob spindle in operative relation with a work blank,the combination of means mounting the hob spindle to the tool slide fordisplacement in the direction of its axis of rotation comprisingshi-ftable hob-spindle bearing means, power means within the tool slideand connected with said bearing means adapted when actuated to shiftsaid bearing means predetermined unit increments of shift whereby toeffect axial displacement of the hob spindle a corresponding distance,control means for said power means responsive to the reciprocatorymovements of the tool slide for rendering said power means effective,said control means including a first counting means and connections forrendering the power means ineffective until a preselected number oftool-slide reciprocations have. been. made, and a second counting meansand connections operative to render said power means ineffective whensaid bearing means has been shifted a preselected number of" unitincrements.

8. The combination of claim 7 including shift-multiplying meansoperatively connected with said control means for the power means toselectively render the power means effective to shift thespindle-bearing means two or more of said unit increments in any onebearingshiftin-g cycle.

9. The combination of claim 7 in which means are also providedelectively to vary the increment of bearing shift imparted to thebearing means by the said power means to a selected fraction of thenormal whole unit increment.

10. The combination of claim 7 including means for varying the incrementof bearing shift imparted by said power means to a selected fraction ofthe normally-available whole-unit of shift and including ashift-multiplying means operatively connected with the said controlmeans for the power means to selectively render the said power meanseffective to shift the spindle-bearing means two or more of saidfractional increments in any one bearingshifting cycle.

11. The combination of a reciprocable slide member adapted to support arotary hob-carrying spindle, bearing means mounting the rotary spindlefor axial movement relative to said slide member, a rack section mountedto said bearing means, a pinion journalled for rotation in said slidemember and meshing with said rack section effective when rotated toimpart axial movement to said bearing means and to the spindle supportedthereby, a power cylinder mounted fixedly relative to said slideenclosing a reciprocably mounted piston and supporting an externallyadjustable calibrated stop means arranged to coact with said powercylinder to limit the stroke of the power cylinder piston to a selectedpredetermined distance, operative connections including a ratchetmechanism between said power cylinder piston and said pinion foractuating said pinion upon the power stroke of said power cylinderpiston, said stop means being so calibrated that adjustment of said stopmeans to each setting produces a different predetermined integerdisplacement of said ratchet mechanism, means for reciprocating saidslide member to cause the hob to perform the hobbing operation, meansresponsive to slide movement for initiating a power stroke of said powercylinder piston and thence a predetermined displacement of said ratchetmechanism to effect a predetermined precise axial movement of thebearing means, and quick change gears in the connections between thepower cylinder piston and said pinion selectively adjustable to modifythe effect of a unit stroke of the power cylinder piston on the axialmovement imparted to the bearing means to a precise predetermined extentfor any given setting of said stop means, whereby differentpredetermined precise axial movements of the spindle may be produced.

12. The combination including a reciprocable slide member, a rotatablehob-carrying spindle, bearing means supporting said spindle for rotationabout its axis, of rotation, bearing displacement means mounted uponsaid slide member operable to displace said bearing means and thespindle supported thereby axially of the spindle relative to said slidemember, a reversible unidirectional intermittent motion deviceoperatively connected to said bearing displacement means and effectivetherethrough to produce precise, predetermined successive displacementsof said spindle in a given direction, cyclically operable actuatormeans, stop means selectively adjustable to determine the desireddistance through which said actuator means is operable in a given cycleto produce a predetermined precise integer displacement of said intermittent motion device, said actuator means being auto: maticallyoperable to displace said intermittent motion device a predeterminedprecise amount according to the setting of said stop means, and quickchange gears interposed between said intermittent motion device and saidbearing displacement means, said quick change gears being selectivelyadjustable to different ratios to achieve desired fractionalmodification of the precise predetermined displacements of said spindleeffected by said actuator means at a given setting of said stop means,where- 'by said spindle may be advanced axially by successivesubstantially identical precisely predetermined amounts.

13. A device as described in claim 12, including dis- 1 6 placementmultiplying means selectively operable to determine the number ofsuccessive uninterrupted operating cycles for said actuator means.

References Cited in the file of this patent UNITED STATES PATENTS1,618,668 Mikaelson Feb. 22, 1927 2,484,856 Purvin Oct. 18, 19492,516,750 Brower July 25, 1950 2,690,701 Zirnmermann et al. Oct. 5, 19502,697,382 Petrie Dec. 21, 1954 2,714,838 Scone Aug. 9, 1955 2,897,728Vasselli Aug. 4, 1959

1. THE COMBINATION OF A TRANSLATABLE SLIDE MEMBER, A HOB SPINDLE, MEANSMOUNTING SAID HOB SPINDLE FOR ROTARY AND AXIAL MOVEMENT RELATIVE TO THESLIDE MEMBER, POWER-OPERATED CLAMPING MEANS FOR SAID SPINDLE-MOUNT INGMEANS NORMALLY OPERATIVE TO RETAIN THE SPINDLEMOUNTING MEANS IN APRESELECTED AXIALLY ADJUSTED POSITION FIRST POWER MEANS FOR ACTUATINGSAID CLAMPING MEANS, SECOND POWER MEANS ADAPTED WHEN ACTUATED TO EFFECTAXIAL MOVEMENT OF SAID MOUNTED MEANS A PRESELECTED UNIT DISTANCE,SELECTIVELY ADJUSTABLE MEANS TO VARY THE PRESELECTED UNIT DISTANCE,INDEPENDENTLY OPERABLE CONTROL MEANS FOR EACH OF SAID FIRST AND SECONDPOWER MEANS, AND A COORDINATING SYSTEM OF CONTROLS RESPONSIVE TOTRANSLATION OF SIAD SLIDE MEMBER AND OPERATIVE NORMALLY TO EFFECTOPERATION OF SAID CONTROL MEANS THROUGH ONE CYCLE INCLUDING UNCLAMPINGOF SAID SPINDLE-MOUNTING MEANS, THEN AXIAL MOVEMENT THEREOF, AND THEN ARECLAMPING OF THE SPINDLE-MOUNTING MEANS TO THE SLIDE MEMBER, ANDADDITIONAL SELECTIVELY OPERABLE MEANS ASSOCIATED WITH SAID SYSTEM OFCONTROLS FOR CAUSING SAID SYSTEM OF CONTROLS TO REPEAT THE AXIALMOVEMENT PORTION OF THE CYCLE TWO OR MORE TIMES TO THEREBY OBTAIN TWO ORMORE PRESELECTED UNIT DISTANCES OF MOVEMENT OF THE MOUNTING MEANS BEFORRECLAMPING OF THE SPINDLE-MOUNTING MEANS.